This invention relates to an unclouded additive useful in the passivation of metals in a catalytic cracking operation. It also relates to the preparation of an additive useful in the passivation of metals in a catalytic cracking operation. It further relates to the cracking of hydrocarbons, particularly the treatment of cracking catalyst with an additive to passivate metals. It still further relates to the preparation of a catalyst composition useful in the presence of metals in a catalytic cracking operation.
Hydrocarbon feedstock containing higher molecular weight hydrocarbons is cracked by contacting it at an elevated temperature with a cracking catalyst whereby distillates such as gasoline and higher boiling hydrocarbon fuels, for example kerosene, diesel fuel, burning oils, fuel oils and the like are produced. Cracking catalyst, when used to crack feedstocks that contain metals, accumulates a deposit of these metals. These metals usually consist of vanadium, iron, and nickel, and this accumulation decreases the yield of gasoline from the cracking operation and increases the yield of hydrogen and coke. Therefore, there is a need for a cracking process or a modified cracking catalyst which will prevent or reduce the deleterious effects of these metal contaminants.
Prior inventions have used antimony compounds to aid in the passivation of metals in these hydrocarbon feed streams. U.S. Pat. No. 4,321,129, incorporated by reference, shows the use of antimony and tin compounds. U.S. Pat. Nos. 4,025,458 and 4,190,552, also incorporated by reference, show antimony compounds alone, are useful for the passivation of metals. With the increased metal content of crude oils today, it is important that the passivation compounds be as inexpensive as possible in order to produce large volumes of gasoline and other higher boiling hydrocarbon fuels in a cost effective manner.
Prior inventions have recognized antimony hydroxyhydrocarbylthiolates as one type of relatively inexpensive antimony compound useful in the passivation of metals, for example see U.S. Pat. Nos. 4,495,064 and 4,507,398. A problem with some antimony hydroxyhydrocarbylthiolates is that they have a cloudy or dark black opaque appearance. While this cloudy appearance does not affect the effectiveness of antimony hydroxyhydrocarbylthiolates as metals passivation additives, the cloudy appearance is objectionable to potential purchasers and can cause operational problems in plants designed to handle clear antimony hydroxyhydrocarbylthiolates, such as where instrumental or visual observations necessary to operate the plant depend on the transmission of light through the antimony hydroxyhydrocarbylthiolate solution.